Time to buy a class D amp?

Hello serhan62,

     I've become a big fan of class D amps through research and personal experience gained by using several examples in my own system.  But I believe all amp types have their pros, cons, compromises and limitations and that class D amps are not the best choice for everyone.
     I believe it's very important to match the amp(s) used to one's speakers while also considering one's personal preferences and tastes.  I understand the truth is that all amp types are capable of providing excellent sound quality and performance results when properly matched to one's speakers but that all amp types are not suitable for all speaker types.  
     I also know that, once an individual discovers a good match between amp(s) and their speakers that performs well and they enjoy the sound quality of or even numerous combinations, I have absolutely no interest or concern in dissuading them from utilizing that combination or combinations.

Tim

Thanks for the post Erik, I had not seen that NP article. There were some good papers in the 70s on current source amps.


I agree with Atmosphere, you can overdamp some speakers. I am not sure I totally agree with your and his explanation wrt how bass notes behave or wrt what is natural, but agree there is an effect and it may not be pleasant.


It's a complex interaction of mechanical resonance, electrical resonance, and mechanical and electrical damping which occurs when you try to stop a woofer faster than it is physically capable of.

audiozenology:" It's a complex interaction of mechanical resonance, electrical resonance, and mechanical and electrical damping which occurs when you try to stop a woofer faster than it is physically capable of."

Hello audiozenology,

     I believe a thorough comprehension of how excessively high damping factors effect bass sound quality requires less concentration on how complex the interaction of forces are and more on the fact that an amp with high damping factors results in it having very firm control over the starting and stopping of a woofer in a conventional dynamic speaker and the bass diaphragm section of a planar-magnetic or electrostatic panel speaker. 
     The critical part is to have a thorough understanding that it's the amp's firm control over the bass transducers that can cause truncated bass tone decays and that a thorough understanding of the exact complex interactions involved are less important. 

Tim

Tim,


In theory the "signal" stops and starts as recorded so that is accurate. The problem is the woofer does not stop right away. In a lower damping factor amp the output resistance will help dissipate the energy in the woofer which can give it a more controlled stop. With a high damping factor all the energy is dissipated in the woofer / crossover. That makes for a different sound.

IMO it is possible to overdamp loudspeakers and thus truncate the bass notes

This statement gives a wrong impression for amplifiers output impedance. That should really be.
There are a small minority of speakers that are "overdamped" by bad design or being purposely overdamped designed, and it's the speaker manufacturer problem to get the "Q" correct. Not because the amp is over-damped or underdamped.
And amps are also supposed to measure as flat as possible regardless of load impedance they see. 

From the Speaker design bible
.707 is said to be the correct "Q" with respect to damping. A higher Q indicates a woofer that is underdamped (loose) while a number lower than .707 indicates an overly damped woofer.

There is no such thing as too low for an amps output impedance. They even build speakers with "driver servo control circuits" to control the bass driver excursions even more and faster than the amps can do.

A classic example of trying to corner the amp/speaker market was the Linn/Naim scam of the 80's when a "purposely overdamped speaker" was mated with a "purposely under damped amp", when together they were a match and sounded good.
When either were substituted for something else and there was either, no bass because of being too tight, or too much soft woolly bass.
When a Krell was substituted for the amp, there was very little bass, (what!!! a Krell with no bass!!) that raised the eyebrows.
Needless to say this idea was Linn/Naim was exposed eventually and they did stopped doing it probably through fear of being called cheats, great marketing idea though if you have no conscience.

Cheers George